The present invention relates to mass transfer and heat exchange columns and, more particularly, to structured packing elements utilized within such columns to facilitate interaction between fluid streams.
Various types of packing elements are commonly used in mass transfer and heat exchange columns to facilitate interaction between fluid streams flowing within the column. Normally, these fluid streams include a downwardly flowing liquid stream and an upwardly flowing vapor stream. One type of packing element used in such columns is commonly referred to as structured packing and comprises a plurality of corrugated plates that are formed from sheet material such as metal. The corrugated plates are arranged in a parallel and upright orientation and are commonly secured together in a bundle commonly referred to as a “brick.” The horizontal cross section of the column is normally filled with one or more bricks and multiple vertically adjacent layers of bricks may be utilized to form a packing bed of a preselected height within one or more regions of the column.
The corrugations of adjacent structured packing plates of the type described above are normally arranged in crisscrossing relationship and extend at a preselected angle, such as 45 or 60 degrees, to the vertical column axis. The corrugations of adjacent plates are normally in contacting relationship, but may also be spaced apart by spacers, an interposed flat plate or other methods. It is also known to arrange the plates with the corrugations of adjacent plates extending in parallel relationship.
Various types of texturing and treatments have been applied to the surface of the above-described corrugated plates to facilitate the mass transfer between the fluid streams and to reduce the pressure drop as the fluid streams flow through the structured packing beds. For example, a plurality of apertures in the plates have been utilized to permit fluid to pass from one side to the other side of each plate and to enhance the lateral spreading of liquid flowing downwardly along the plate surfaces. Rows of horizontally extending grooves are also utilized to facilitate the lateral spreading of the descending liquid. In another example, described in U.S. Pat. No. 4,740,334 to Rukovena, Jr., rows of hollow cone shaped protuberances with perforated peaks are formed in the corrugated plates and are said to cause more uniform wetting of the surface of the plates. The perforated peaks have small openings that are formed by small slits in the wall of the peak. These openings are described as being smaller in area and size than the opposed inlet to the cone shaped protuberance.
Although the surface texturing and treatments of the types described above may increase the efficiency of the packing plates, further improvements in efficiency are desired.
Sheets of perforated metal have also been used as part of a composite material usable for producing gaskets. In U.S. Pat. No. 5,172,920 to Schlenk, the metal sheet is perforated with a plurality of square holes, each of which is bordered by a set of four triangular tangs that are flared outwardly with respect to the hole. While the specific construction of the perforated metal sheet is described as useful as a gasket material substrate, there is no suggestion that the perforated metal sheet might be used as a structured packing.